Sarcoidosis is a multisystem granulomatous inflammatory disease of unknown etiology. Hereditary susceptibility to sarcoidosis is suggested by reports of familial clustering and a higher prevalence in certain ethnic groups, particularly African-Americans. The objectives of this study are to determine if hereditary susceptibility predisposes African-Americans to sarcoidosis and to identify sarcoidosis susceptibility genes in African-Americans. We plan to test for association of sarcoidosis with markers for candidate genes using the affected-family-based-control method and to perform a segregation analysis in order to test simultaneously for possible environmental risk factors and genetic mechanisms of disease transmission.